This project is designed to determine the mechanisms responsible for amino acid induced orotic aciduria in animals. The present studies are using the technique of bicarbonate incorporation into urea and orotic acid to determine the influence of various amino acids of both metabolic pathways. These studies are aimed at determining the influence of amino acid imbalances upon dietary arginine requirements plus the capacity of the urea cycle to detoxify ammonia. By examining the relative rate of biocarbonate incorporation in orotic acid and urea, one can determine if the imbalance is created by increased amino acid degradation or a direct inhibitory effect upon the urea cycle. These studies will examine the influence of excess dietary intakes of various amino acids on their ability to alter urea and pyrimidine biosynthesis. These studies will also examine the influence of parenteral solution containing imbalanced amino acid mixtures on the laboratory rat's ability to detoxify ammonia.